THE RING IMAGING CHERENKOV DETECTOR OF DELPHI

The ring imaging Cherenkov detector system in the DELPHI experiment at the Large Electron-Positron storage ring at CERN, is designed to do particle identification over most of the solid angle in the momentum range from ∼2 GeV c to ∼40 sol GeV c . Two radiator media are used to cover the momentum range; (i) a 1 cm layer of liquid C6F14, and (ii) a volume filled with gaseous C5F12 or C4F10. Photosensitive time projection chambers record the conversion points of the ultraviolet photons produced in both radiator systems. The total active area is ∼30 m2 in the barrel region and ∼8 m2 in the two endcaps. The design of the detector systems is described in this paper. We will also report performance figures and compare them to simulation studies.